Pre Populate Or Add Items To A Cart Or Order

If a customer wants help ordering can I as admin add items or pre populate their Cart for them.  If so how do I do that or add items to an existing cart.  I know how to convert their cart to an order, but I cant find a way to add items

They would need an account. Then  view their account in the admin and in the Actions tab select Login as customer.

Then you will be logged in as that customer and you can add things to cart. When you are done be sure to logout of the customer side.

Thank you